Alkyl glycosides are compounds comprising a carbohydrate and an alcohol, chemically bound in a cyclic acetal. Compounds involving alkyl groups exceeding C5 belong to a class of compounds called glycolipids, which are commonly known to show surfactant properties and have acquired some industrial impact for special application fields. Their role in biology is widely acknowledged.
Most of the applications for synthetic glycolipids rest on their molecular properties as described in U.S. Pat. Nos. 3,219,656, 3,547,828, 3,839,318 and EP 041960. These properties fall into two broad categories: adsorption and self assembly. The first indicates interfacial properties on water/oil, water/air or solid/gas interfaces. Connected applications are focusing on wetting, foaming, detergency and emulsions. The most important industrial roles of surfactants are connected with the formation of emulsions and with detergency. An emulsion is a dispersion of two normally immiscible fluids; thus emulsions are multiphase systems even though they might appear to look homologue. Detergency is responsible for most cleaning purposes. Both rheology (flow properties) and kinetics of mesophase formation (any non crystalline kind of self assembly of matter) in surfactant systems has high potential impact on manufacturing processes, since rheology might limit the handling of processes. Self assembly is the ability of matter to form supramolecular structures. Examples cover micelles, bilayers and other liquid crystals which all may exhibit applications on their own.
The liquid crystalline behavior of alkyl glycosides has been subject to several investigations (e.g. D. E. Koeltzow et al., J. Am. Oil Chem. Soc., 1984, 61, 1651; V. Vill et al., Liq. Cryst., 1989, 6, 349-356). However, while carbohydrate derived compounds have been found useful as additives for liquid crystal based switches with respect to their high optical twisting power (V. Vill et al., Z. Naturforschung A, 1989, 44, 675-679), alkyl glycosides so far did not acquire usage for liquid crystal applications. Their liquid crystal phase temperature range resemble a major disadvantage. Pure compounds exhibit liquid crystallinity only at temperatures higher than ambient temperature. Most technical applications, however, require (or at least favor) lower temperatures. The present invention enables the formation of liquid crystal phases for alkyl glycosides at room temperature.
The use of alkyl glycosides for surfactant purposes has been described in several patents and papers (e.g. U.S. Pat. No. 9,908,517, WO 0190286). Suitable applications cover the use as detergent for cleaning purposes (e.g. U.S. Pat. No. 5,858,954, MY 106677) as well as additives for e.g. cosmetic formulations (e.g. WO 9406408, U.S. Pat. No. 5,605,651, JP 9173822). A related example for usage in vesicles may be found in German Patent DE 1963437. Commonly alkyl glycosides (also named APGs, or alkyl polyglycosides) contain only one single alkyl chain. This way they differ from natural lipids, which exhibit a double chain structure, involving a polar head-group and two non-polar chains. These structures, showing special physical characteristics generally believed to be responsible for the properties of biological membranes, cannot be mimicked by simple APGs.
For biophysical studies, therefore, more complex compounds, like glycoglycerolipids, are needed. Due to immense problems involved in lipid purification, generally synthetic compounds are favored over natural derived material. The number of chemical transformations involved and the extensive purification, however, make this approach expensive and limits future applications. A major obstacle is based on the limited chemical stability of the ester groups present in glycoglycerolipids. These add to both purification requirements and the number of chemical steps. While syntheses for ether analog structures have been published (e.g. H. Minamikawa et al., Chem. Phys. Lipids, 1994, 72, 111-118), improving the accessibility of materials, a more easy access to model compounds remains desirable. The present invention provides such a possibility.
Branched chain (guebert type) alcohol derived esters have been applied as emulsifiers before, showing superior emulsification and better liquidity (e.g. U.S. Pat. Nos. 5,717,119, 5,736,571, 6,013,813). The effect of branching on alcohols bond in glycosides, however, has not been investigated before.
Synthetic glycolipids exhibit a large spectrum of useful applications such as coating a drug to keep it from early destruction, stabilization of hydrocarbon foam, primary solvents for tropical medication, mild soap for delicate fields of application or the synthesis of nanostructure materials. Prior art Japanese Patent JP 11244608 even disclosed the usage of glycolipid derivatives as antifoaming additives for resin manufacturing, dyeing and wastewater treatment.
The objective of the invention is to provide new glycolipids showing special liquid crystal properties with respect to thermotropic and lyotropic behavior. Possible applications of these glycolipids involve:                low temperature liquid crystals, e.g. for optical switches and other applications        artificial membranes        drug coating and related pharmaceutical applications (e.g. vesicles)        surfactant and micelle applications in cosmetics, detergency and nanotechnology        antifoaming surfactants for process- and wastewater treatments        